Companies in the wireless communications infrastructure market compete on, among other things, system availability. System availability includes not only minimal downtime but also the ability to detect and resolve system problems before such problems become apparent to the users of the system. To facilitate the early detection of system problems, the infrastructure systems typically include alarm systems that will detect a failure in the infrastructure system and generate an alarm signal indicating such failure. The infrastructure system may then be remotely monitored for the presence of such alarm signals. Since the infrastructure typically comprises multiple geographically-diverse base sites, the ability to remotely monitor system failures is a highly desirable feature of an infrastructure system.
A wireless communications infrastructure typically includes at least one base site. A base site generally includes an inbound radio frequency (RF) portion that typically includes multiple antennas, an RF distribution system, and at least one base station. Each antenna is connected via a cable to the RF distribution system, and the RF distribution system is in turn connected via cables to the base station. The RF distribution system typically comprises multiple bandpass filters, each connected by cable to a signal splitter. In a typical wireless communication system, a low power RF signal transmitted by a mobile or portable communication unit is received by the multiple antennas. Each antenna conveys the received RF signal to a bandpass filter, which filters the desired signal from undesired signals. The filter then conveys the filtered signals to a signal splitter, which splits the received signal into multiple equal amplitude signals. Each of the equal amplitude signals is then conveyed to a base station. Each base station includes one or more receivers that can receive the RF signal from the splitter, demodulate the RF signal, and route the RF signal to a transmitter for rebroadcast or to a telephone interconnect device or other wireline destination.
Failures in the inbound portion of a base site are remotely detected by use of alarm systems that monitor the bias of active RF devices. Generally, an alarm signal is generated when the bias of an active device shifts outside of an acceptable range. However, the alarm systems provide very limited coverage of the variety of potential failures in the inbound portion and often will not detect many configuration or installation errors, open circuits or short circuits in the RF lineup, or cable failures or improper connections. For example, the alarm system will not distinguish between a base station that is inactive due to the absence of a received signal in the inbound portion and a base station that is inactive due to an improperly connected cable in the inbound portion that prevents a received RF signal from being conveyed to the base station.
One method of determining such a system failure is to wait for a customer complaint with respect to system performance and then to bring test equipment to the base site to manually check the inbound portion of the site. However, this angers customers and is time consuming and labor intensive. Another method of determining such a failure is to set up a separate test site containing a calibrated transmitter, which transmitter would transmit a calibrated test signal. The received test signal could then be analyzed at the base site. However, this requires an additional investment in infrastructure equipment.
Therefore a need exists for a method and apparatus that will provide improved detection of failures in the inbound portion of a wireless communication infrastructure prior to the advent of customer complaints and that does not require an investment in additional infrastructure equipment.